The present invention relates generally to compression release arrangements and more particularly to an improved compression release mechanism for an internal combustion engine, for example of the two-stroke cycle variety.
In the illustrative environment of a two-stroke cycle internal combustion engine, U.S. Pat. No. 3,417,740 to Perlewitz, illustrates an automatic compression release mechanism. This known compression release mechanism employs a pair of independently operable reed valves at inlet and outlet ports, respectively, of a compression release chamber. The compression release chamber inlet port is coupled to the engine combustion chamber while the compression release chamber outlet port is coupled to the engine exhaust system. An arrangement for slowly releasing the pressure in the compression release chamber to the atmosphere so that the outlet reed valve assumes the open position when the engine is stopped is also included in this known patented device. In this known compression release device, the two reed valves are separate pieces, separately mounted, and the compression release exhaust port is ducted to the engine exhaust system while the arrangement for slowly leaking or bleeding pressure from the compression release mechanism is ducted to the atmosphere.
While this known compression release mechanism has met with considerable commercial success, the compression release function sometimes deteriorates and may cease to function in warm weather applications, such as lawnmowers, because the passage to the zone of lower pressure, such as the exhaust passage of the engine, sometimes plugs with combustion deposits. Further, the cost of this known compression release arrangement, while not prohibitive, is higher than desirable.